CN113701676B - Stray light measuring device and method - Google Patents
Stray light measuring device and method Download PDFInfo
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- CN113701676B CN113701676B CN202110882670.0A CN202110882670A CN113701676B CN 113701676 B CN113701676 B CN 113701676B CN 202110882670 A CN202110882670 A CN 202110882670A CN 113701676 B CN113701676 B CN 113701676B
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
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- G01B11/30—Measuring arrangements characterised by the use of optical techniques for measuring roughness or irregularity of surfaces
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Abstract
The application relates to a stray light measuring device and method, which utilizes a laser to output laser. The output laser enters the acousto-optic frequency shift unit for frequency shift through the spectroscope and the collimating lens. And focusing the frequency-shifted light on the surface of the object to be measured through the collecting lens. Then, impurities on the surface of the object to be measured are collected by using a collecting lensAstigmatism. The collected stray light returns to the laser cavity of the laser through the acousto-optic frequency shift unit, the collimating lens and the spectroscope and generates self-mixing interference with the laser in the cavity. The interference light after mixed interference enters the signal demodulation processor through the spectroscope so as to detect the level of stray light on the surface of the object to be detected. The gain factor specific to laser feedback can amplify weak signals, usually up to 10 6 After the self-mixing interference occurs, the laser emitted by the laser again contains the information of the stray light level on the surface of the object to be measured, and the stray light level on the surface of the object to be measured can be obtained by sending the information into the signal processing unit.
Description
Technical Field
The application relates to the field of detection of optical elements with ultra-smooth surfaces, in particular to a stray light measuring device and a method.
Background
An ultra-smooth surface optical element refers to an element with a surface roughness less than 1nmRMS (roughness root mean square), and with the continuous development of modern industry, the element is widely applied to the fields of laser gyro, nuclear fusion, ultra-precision machining and manufacturing and the like due to good smoothness.
The optical element with the ultra-smooth surface can be manufactured by the technology such as magnetorheological technology, but besides the processing and manufacturing technology, the detection technology is also a key factor for restricting the development of the field. The effective detection of the extremely weak stray light signal on the surface of the element can determine whether the element meets the use requirement, and the traditional detection method is mainly based on a microscopic imaging system or heterodyne interference. The microscopic imaging system comprises a high-precision microscope such as an atomic force microscope and the like, the cost is very high, the structure is complex, and the operation is carried out by professional personnel, moreover, the system mostly focuses on the surface appearance, the detection efficiency is low, the surface of an element is easily damaged, and the working distance is generally short; the traditional heterodyne interference can not effectively detect the power 10 which is weaker than the incident light -10 The magnitude of stray light focuses on the surface appearance, the test period is long, and the actual industrial production requirements are not met.
Disclosure of Invention
In view of the above, the present application provides a stray light measuring apparatus and method. The device and the method are also suitable for detecting the ultra-weak light signals.
The application provides a stray light measuring device, includes:
a laser for outputting laser light;
the spectroscope is arranged on a laser light path of the laser;
the collimating lens is arranged in the transmission light direction of the spectroscope;
the acousto-optic frequency shift unit is used for shifting the frequency of the collimated light passing through the collimating lens;
the collecting lens is arranged between the acousto-optic frequency shift unit and the object to be detected, and is used for focusing the frequency shift light passing through the acousto-optic frequency shift unit and collecting stray light on the surface of the object to be detected; and
and the signal demodulation processor is arranged in the direction of the reflected light of the spectroscope, the collected stray light returns to the laser cavity of the laser through the acousto-optic frequency shift unit, the collimating lens and the spectroscope and generates self-mixing interference with laser in the cavity, and the interference light after the self-mixing interference enters the signal demodulation processor through the spectroscope so as to detect the level of the stray light on the surface of the object to be detected.
In one embodiment, the distance between the collecting lens and the object to be measured is a set distance, so that the focal point of the collecting lens is focused on the surface of the object to be measured.
In one embodiment, the angle between the object to be measured and the horizontal plane is a set angle, so that the reflected light on the surface of the object to be measured does not pass through the collecting lens.
In one embodiment, the acousto-optic frequency shift unit comprises a first acousto-optic frequency shifter and a second acousto-optic frequency shifter for differentially shifting the collimated light of the collimating lens.
In one embodiment, the signal demodulation processor comprises:
the photoelectric detector is arranged in the direction of the reflected light of the spectroscope, detects an optical signal with the information of the level of the stray light on the surface of the object to be measured, and converts the optical signal into an electric signal; and
and the signal processing unit is electrically connected with the photoelectric detector and is used for demodulating the electric signal so as to detect the level of the stray light on the surface of the object to be detected.
In one embodiment, the laser is a solid state laser, a semiconductor laser, or a fiber laser.
Based on the same inventive concept, the application provides a stray light measuring method, which comprises the following steps:
outputting laser by a laser;
the output laser enters an acousto-optic frequency shift unit for frequency shift through a spectroscope and a collimating lens;
focusing the frequency-shifted light on the surface of an object to be measured through a collecting lens;
collecting stray light on the surface of the object to be measured by using the collecting lens;
the collected stray light returns to the laser cavity of the laser through the acousto-optic frequency shift unit, the collimating lens and the spectroscope and generates self-mixing interference with laser in the cavity;
and the interference light after mixed interference enters a signal demodulation processor through the spectroscope so as to detect the level of stray light on the surface of the object to be detected.
In one embodiment, the step of focusing the frequency-shifted light on the surface of the object to be measured through the collecting lens includes:
and adjusting the distance between the collecting lens and the object to be measured to be a set distance so as to focus the focus of the collecting lens on the surface of the object to be measured.
In one embodiment, the method further comprises the following steps:
and adjusting the angle between the object to be measured and the horizontal plane to be a set angle so that the reflected light on the surface of the object to be measured does not pass through the collecting lens.
In one embodiment, the step of detecting the level of the stray light on the surface of the object to be measured by entering the mixed interfered interference light into the signal demodulation processor through the spectroscope includes:
detecting an optical signal with information of the level of the stray light on the surface of the object to be detected by using a photoelectric detector, and converting the optical signal into an electric signal;
and demodulating the electric signal by using a signal processing unit so as to detect the level of stray light on the surface of the object to be detected.
The stray light measuring apparatus and method output laser light by using a laser. The output laser enters the acousto-optic frequency shift unit for frequency shift through the spectroscope and the collimating lens. And focusing the frequency-shifted light on the surface of the object to be measured through the collecting lens. And then, collecting the stray light on the surface of the object to be measured by using a collecting lens. The collected stray light returns to the laser cavity of the laser through the acousto-optic frequency shift unit, the collimating lens and the spectroscope and generates self-mixing interference with laser in the cavity. And the interference light after mixed interference enters a signal demodulation processor through the spectroscope so as to detect the level of stray light on the surface of the object to be detected. The gain factor specific to laser feedback can amplify weak signals, usually to 10 6 After the self-mixing interference occurs, the laser emitted by the laser again contains the information of the stray light level on the surface of the object to be measured, and the stray light level on the surface of the object to be measured can be obtained by sending the information into the signal processing unit. The laser feedback based weak stray light signal detection device has the advantages that the non-contact type high-efficiency detection of the weak stray light signal on the super-smooth surface is realized on the basis of the laser feedback principle and the effective collection of the stray light, the cost is low, the structure is simple, and the sensitivity is high.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a stray light measuring apparatus according to an embodiment of the present disclosure;
fig. 2 is a schematic diagram of an implementation of an optical splitter and frequency shift unit according to an embodiment of the present application.
Description of the main drawing elements
1-a laser; 2-a spectroscope; 3-a collimating lens; 4-a first acousto-optic frequency shifter; 5-a second acousto-optic frequency shifter; 6-acousto-optic frequency shift unit; 7-a collecting lens; 8-the substance to be detected; 9-a photodetector; 10-a signal processing unit; 11-signal demodulation processor.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present application more comprehensible, embodiments accompanying the present application are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. This application is capable of embodiments in many different forms than those described herein and those skilled in the art will be able to make similar modifications without departing from the spirit of the application and it is therefore not intended to be limited to the embodiments disclosed below.
It will be understood that, as used herein, the terms "first," "second," and the like may be used herein to describe various elements, but these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first acquisition module may be referred to as a second acquisition module, and similarly, a second acquisition module may be referred to as a first acquisition module, without departing from the scope of the present application. The first acquisition module and the second acquisition module are both acquisition modules, but are not the same acquisition module.
It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The application provides a stray light measuring device, which comprises a laser 1, a spectroscope 2, a collimating lens 3, an acousto-optic frequency shift unit 6, a collecting lens 7 and a signal demodulation processor 11.
The laser 1 is used to output laser light. The spectroscope 2 is arranged on a laser light path of the laser 1. The beam splitter 2 is used for splitting the output laser into two paths, wherein one path of projected light is sent to the collimating lens 3, and the other path of reflected light is sent to the signal demodulation processor 11. The collimating lens 3 is arranged in the transmission light direction of the spectroscope 2. The collimating lens 3 is used for collimating one path of transmission light of the spectroscope 2 and sending collimated laser into the acousto-optic frequency shift unit 6. The acousto-optic frequency shift unit 6 is used for shifting the frequency of the collimated light passing through the collimating lens 3. The collecting lens 7 is arranged between the acousto-optic frequency shift unit 6 and the object to be measured 8, and is used for focusing the frequency shift light passing through the acousto-optic frequency shift unit 6 and collecting the stray light on the surface of the object to be measured. The signal demodulation processor 11 is arranged in the direction of the reflected light of the spectroscope 2, the collected stray light returns to the laser cavity of the laser 1 through the acousto-optic frequency shift unit 6, the collimating lens 3 and the spectroscope 2 and undergoes self-mixing interference with laser in the cavity, and the interference light after the self-mixing interference enters the signal demodulation processor 11 through the spectroscope 2 so as to detect the level of the stray light on the surface of the object to be detected.
It is to be understood that the type of the laser 1 is not particularly limited. In an alternative embodiment, the laser 1 is a solid state laser, a semiconductor laser or a fiber laser.
A solid-state laser is a laser using a solid-state laser material as a working substance. The working medium is a crystal or glass as a matrix material, which is uniformly doped with a small amount of active ions. For example, a laser incorporating trivalent neodymium ions in a Yttrium Aluminum Garnet (YAG) crystal may emit near-infrared laser light having a wavelength of 1050 nm. The solid laser has the characteristics of small volume, convenient use and high output power. The continuous power of the solid laser is generally over 100 watts, and the pulse peak power can be as high as 10W.
Semiconductor lasers, also known as laser diodes, are lasers that use semiconductor materials as the working substance. Due to the difference in material structure, the specific process of generating laser light in different types is more specific. Common working substances are gallium arsenide (GaAs), cadmium sulfide (CdS), indium phosphide (InP), zinc sulfide (ZnS), and the like. The excitation mode includes three modes of electric injection, electron beam excitation and optical pumping. The semiconductor laser 1 can be divided into homojunction, single heterojunction, double heterojunction and the like. Most of the homojunction laser 1 and the single heterojunction laser 1 are pulse devices at room temperature, and the double heterojunction laser 1 can realize continuous work at room temperature.
Semiconductor diode lasers are the most practical and important class of lasers. It has small size and long service life, can be pumped by adopting a simple current injection mode, and has the working voltage and current compatible with an integrated circuit, so that the integrated circuit can be monolithically integrated with the integrated circuit. And may also be directly current modulated at frequencies up to GHz to obtain high speed modulated laser output.
The Fiber Laser is a Laser formed by using a doped Fiber doped with various rare earth element ions as a working substance and utilizing the nonlinear self-phase modulation effect of the Fiber on the basis of the Fiber. The optical fiber laser is a multi-wavelength light source and consists of a gain medium, an optical resonant cavity and a pumping source. The gain medium generates photons, the optical resonant cavity can feed back the photons, and the pumping source can excite photon transition. The fiber laser has the advantages of low threshold value, high power, high beam quality, good reliability, compact structure, good heat dissipation and the like.
In one possible embodiment, the laser 1 is a microchip solid state laser. The laser output by the microchip solid laser can be linearly polarized light, and the mode is a fundamental transverse mode and a single longitudinal mode.
It is understood that the specific structure of the acousto-optic frequency shift unit 6 is not limited as long as the collimated light passing through the collimating lens 3 can be frequency shifted. In one possible implementation, the acousto-optic frequency shifter unit 6 includes a first acousto-optic frequency shifter 4 and a second acousto-optic frequency shifter 5 for differentially shifting the collimated light passing through the collimating lens 3. Referring to fig. 2, when laser is diffracted by the ultrasonic grating through the acousto-optic medium, the propagation direction and frequency of the laser will change. The frequency of the diffracted light superimposes an ultrasonic frequency on the original input laser frequency, which is the acousto-optic shift frequency. The amount of change in the optical frequency is equal to the frequency of the applied rf power signal. When the output light is the positive first-order diffraction light, the frequency of the output light is the frequency of the electrical signal of the original laser frequency. By changing the frequency of the input electrical signal, the amount of frequency shift of the output light can be controlled. Since the acousto-optic frequency shifter requires the output light power as high as possible in practical use, the acousto-optic frequency shifter generally operates in a bragg diffraction mode. A part of laser light is split from a laser beam emitted by the laser 1 and passes through the acousto-optic frequency shifter, and after the laser light interacts with ultrasonic waves through the acousto-optic device, the frequency of diffracted light of the laser light is the superposition of the frequency of the laser light and the frequency of the ultrasonic waves, so that the diffracted light has the frequency shift amount with the same frequency as the ultrasonic waves. The other part of laser which does not pass through the acousto-optic frequency shifter irradiates the surface of the object 8 to be measured, the scattered light is subjected to Doppler frequency shift and then is subjected to beat with the diffracted light, the beat frequency can be greatly reduced, even the zero beat can be realized, the Doppler frequency shift can be conveniently measured by measuring the frequency of an electric signal added on the acousto-optic frequency shifter, and therefore the speed measuring range and the measuring precision of the laser velocimeter are greatly enlarged.
It is to be understood that the specific structure of the signal demodulation processor 11 is not particularly limited as long as the detection of the stray light level on the surface of the object to be measured can be achieved. In one possible implementation, the signal demodulation processor 11 includes a photodetector 9 and a signal processing unit 10. The photodetector 9 is disposed in the direction of the reflected light of the beam splitter 2. The photodetector 9 is used for detecting an optical signal carrying information of the stray light level on the surface of the object to be measured and converting the optical signal into an electrical signal. The signal processing unit 10 is electrically connected to the photodetector 9, and is configured to demodulate the electrical signal to detect the level of stray light on the surface of the object to be detected.
In the stray light measuring apparatus, the laser 1 outputs laser light. The output laser enters the acousto-optic frequency shift unit 6 for frequency shift through the spectroscope 2 and the collimating lens 3. The frequency-shifted light is focused on the surface of the object to be measured through the collecting lens 7. Then, stray light on the surface of the object to be measured is collected by the collecting lens 7. The collected stray light passes through the acousto-optic frequency shift unit 6 and the collimating lens3 and the spectroscope 2 return to the laser cavity of the laser 1 and generate self-mixing interference with the laser in the cavity. The interference light after mixed interference enters the signal demodulation processor 11 through the spectroscope 2 to detect the level of stray light on the surface of the object to be detected. The gain factor specific to laser feedback can amplify weak signals, usually up to 10 6 After the self-mixing interference occurs, the laser emitted again by the laser 1 contains the information of the stray light level on the surface of the object to be measured, and the stray light level on the surface of the object to be measured can be obtained by sending the information into the signal processing unit 10. The method and the device realize non-contact efficient detection of the weak stray light signal of the super-smooth surface based on the laser feedback principle and effective collection of the stray light. This application has adopted the structure of receiving and dispatching integral type, greatly reduced the complexity of system, simultaneously the cost is reduced.
In one embodiment, the distance between the collecting lens 7 and the object 8 is a set distance, so that the focal point of the collecting lens 7 is focused on the surface of the object. It is understood that, in order to collect the stray light on the surface of the object to be measured to the maximum, the focal point of the collecting lens 7 can be focused on the surface of the object to be measured. Specifically, the position of the object 8 to be measured may be determined, and then the collecting lens 7 may be disposed between the object 8 to be measured and the acousto-optic frequency shift unit 6, and the distance between the collecting lens 7 and the object 8 is a set distance so that the focal point of the collecting lens 7 is focused on the surface of the object to be measured.
In one embodiment, in order to avoid the influence of the reflected light of the object 8 on the stray light of the object 8, and to improve the detection accuracy, the angle between the object 8 and the horizontal plane is set to be a predetermined angle, so that the reflected light on the surface of the object does not pass through the collecting lens 7. Specifically, after the relative positions of the object 8 and the collecting lens 7 are determined, the angle of the object 8 can be adjusted so that the reflected light from the surface of the object is not collected by the collecting lens 7, but the scattered light from the surface of the object is collected by the collecting lens 7. It is understood that, if the information of the reflected light needs to be detected, the angle of the object 8 to be measured is not limited, and the reflected light is returned to the laser cavity.
Based on the same inventive concept, the application provides a stray light measuring method. The stray light measuring method comprises the following steps:
outputting laser by using a laser 1;
the output laser enters an acousto-optic frequency shift unit 6 for frequency shift through a spectroscope 2 and a collimating lens 3;
the frequency-shifted light is focused on the surface of an object to be measured through a collecting lens 7;
collecting stray light on the surface of the object to be measured by using the collecting lens 7;
the collected stray light returns to the laser cavity of the laser 1 through the acousto-optic frequency shift unit 6, the collimating lens 3 and the spectroscope 2, and self-mixing interference is generated between the stray light and laser in the cavity;
the interference light after mixed interference enters the signal demodulation processor 11 through the spectroscope 2 to detect the level of stray light on the surface of the object to be detected.
In one embodiment, the step of focusing the frequency-shifted light on the surface of the object to be measured through the collecting lens 7 includes:
and adjusting the distance between the collecting lens 7 and the object to be measured 8 to be a set distance so as to focus the focus of the collecting lens 7 on the surface of the object to be measured.
In one embodiment, the method further comprises the following steps:
and adjusting the angle between the object to be measured 8 and the horizontal plane to be a set angle so that the reflected light on the surface of the object to be measured does not pass through the collecting lens 7.
In one embodiment, the step of detecting the level of the stray light on the surface of the object to be measured by entering the mixed interfered interference light into the signal demodulation processor 11 through the spectroscope 2 includes:
detecting an optical signal with information of the level of the stray light on the surface of the object to be detected by using a photoelectric detector 9, and converting the optical signal into an electric signal;
the electrical signal is demodulated by a signal processing unit 10 to detect the level of stray light on the surface of the test object.
The stray light measuring method uses a laser 1And outputting laser. The output laser enters the acousto-optic frequency shift unit 6 for frequency shift through the spectroscope 2 and the collimating lens 3. The frequency-shifted light is focused on the surface of the object to be measured through the collecting lens 7. Then, stray light on the surface of the object to be measured is collected by the collecting lens 7. The collected stray light returns to the laser cavity of the laser 1 through the acousto-optic frequency shift unit 6, the collimating lens 3 and the spectroscope 2, and generates self-mixing interference with the laser in the cavity. The interference light after mixed interference enters the signal demodulation processor 11 through the spectroscope 2 to detect the level of stray light on the surface of the object to be detected. The gain factor specific to laser feedback can amplify weak signals, usually up to 10 6 After the self-mixing interference occurs, the laser emitted again by the laser 1 contains the information of the stray light level on the surface of the object to be measured, and the stray light level on the surface of the object to be measured can be obtained by sending the information into the signal processing unit 10. The system is based on the laser feedback principle and realizes non-contact efficient detection of the weak stray light signal of the super-smooth surface by effectively collecting the stray light, and is low in cost, simple in structure and high in sensitivity.
The procedure for carrying out the above-described measuring method is illustrated by way of example by the stray light measuring device shown in fig. 1:
confirm 8 positions of determinand, open 1 power of laser instrument and reputation frequency shifter drive power supply, place the position with above-mentioned collection lens 7, make its focus to the determinand surface, when laser irradiation determinand surface, the specular reflection takes place, obey the reflection law, adjust 8 angles of determinand, make the reverberation can not be collected by collection lens 7, the scattering takes place simultaneously, the scattered light is collected by collection lens 7 and is passed through the reputation frequency shifter again, then pass through collimating lens 3 and spectroscope 2, get back to the laser intracavity, take place from mixing interference with the laser of intracavity portion, later outgoing, the laser intensity of outgoing is:
in the above formula, Δ I is the variation value of the output light intensity of the laser 1, and I is the time when the laser 1 is stableThe output light intensity of the laser is G (2 omega) is a feedback gain coefficient, the relaxation oscillation frequency of the laser 1 is related to the frequency shift quantity, omega is the differential frequency shift quantity of the first acousto-optic frequency shifter 4 and the second acousto-optic frequency shifter 5, the total frequency shift quantity is 2 omega because the laser carries out differential frequency shift twice, kappa represents the feedback coefficient of the object and is positively related to the stray light level of the object,
representing a fixed amount of phase offset. From the above formula, it can be seen that the gain coefficient G specific to laser feedback can amplify a weak signal, which can be generally 10 6 The output light of the laser 1 is reflected by the spectroscope 2 and enters the photoelectric detector 9, the optical signal is converted into an electric signal, the amplitude of the signal can represent the level of the stray light of the detected object 8, and the level of the stray light on the surface of the unknown object can be measured by calibrating in advance and drawing a corresponding curve of the signal amplitude and the level of the stray light.
The present application provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the step of demodulating an electrical signal to detect the stray light level on the surface of the object to be measured as described in any of the above embodiments when executing the computer program.
The memory, as a computer-readable storage medium, may be used to store software programs, computer-executable programs, and modules, such as program instructions/modules corresponding to the method for detecting lithium desorption during battery charging in the embodiments of the present application. The processor executes various functional applications and data processing of the device by running software programs, instructions and modules stored in the memory, that is, the step of demodulating the electrical signal to detect the stray light level on the surface of the object to be measured is realized.
The memory may mainly include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application program required for at least one function. The storage data area may store data created according to the use of the terminal, and the like. Further, the memory may include high speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some examples, the memory may further include memory located remotely from the processor, and these remote memories may be connected to the device over a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent application shall be subject to the appended claims.
Claims (10)
1. A stray light measuring apparatus, comprising:
a laser for outputting laser light;
the spectroscope is arranged on a laser light path of the laser;
the collimating lens is arranged in the transmission light direction of the spectroscope;
the acousto-optic frequency shift unit is used for shifting the frequency of the collimated light passing through the collimating lens;
the collecting lens is arranged between the acousto-optic frequency shift unit and the object to be detected, and is used for focusing the frequency shift light passing through the acousto-optic frequency shift unit and collecting stray light on the surface of the object to be detected;
the angle between the object to be measured and the horizontal plane is a set angle, so that the reflected light on the surface of the object to be measured does not pass through the collecting lens; and
and the signal demodulation processor is arranged in the direction of the reflected light of the spectroscope, the collected stray light returns to the laser cavity of the laser through the acousto-optic frequency shift unit, the collimating lens and the spectroscope and generates self-mixing interference with laser in the cavity, the interference light after the self-mixing interference enters the signal demodulation processor through the spectroscope, and the stray light level on the surface of the object to be detected is detected by detecting the light intensity of the interference light.
2. The stray light measuring apparatus according to claim 1, wherein a distance between the collecting lens and the object is a set distance so that a focal point of the collecting lens is focused on the surface of the object.
3. The stray light measuring apparatus according to claim 1, wherein the acousto-optical frequency shift unit includes a first acousto-optical frequency shifter and a second acousto-optical frequency shifter for differentially shifting the collimated light passed through the collimator lens.
4. A stray light measuring apparatus according to claim 1, wherein said signal demodulation processor comprises:
the photoelectric detector is arranged in the direction of the reflected light of the spectroscope, detects an optical signal with the information of the level of the stray light on the surface of the object to be measured, and converts the optical signal into an electric signal; and
and the signal processing unit is electrically connected with the photoelectric detector and is used for demodulating the electric signal so as to detect the level of the stray light on the surface of the object to be detected.
5. A stray light measuring apparatus according to claim 1, wherein the laser is a solid state laser, a semiconductor laser or a fiber laser.
6. A stray light measuring apparatus according to claim 5, wherein the laser light output from said solid state laser is linearly polarized light.
7. A stray light measuring apparatus according to claim 5, wherein the modes of the solid state laser are a fundamental transverse mode and a single longitudinal mode.
8. A stray light measuring method, comprising:
outputting laser by using a laser;
the output laser enters an acousto-optic frequency shift unit for frequency shift through a spectroscope and a collimating lens;
focusing the frequency-shifted light on the surface of an object to be measured through a collecting lens;
collecting stray light on the surface of the object to be measured by using the collecting lens;
adjusting the angle between the object to be measured and the horizontal plane to be a set angle so that the reflected light on the surface of the object to be measured does not pass through the collecting lens;
the collected stray light returns to the laser cavity of the laser through the acousto-optic frequency shift unit, the collimating lens and the spectroscope and generates self-mixing interference with laser in the cavity;
and the interference light after mixed interference enters a signal demodulation processor through the spectroscope, and the stray light level on the surface of the object to be detected is detected by detecting the light intensity of the interference light.
9. A stray light measuring method according to claim 8, wherein the step of focusing the shifted frequency light onto the surface of the object via a collecting lens comprises:
and adjusting the distance between the collecting lens and the object to be measured to be a set distance so as to focus the focus of the collecting lens on the surface of the object to be measured.
10. The stray light measuring method according to claim 8, wherein the step of mixing the interfered interference light into a signal demodulation processor via the beam splitter to detect the stray light level on the surface of the object comprises:
detecting an optical signal with information of the level of the stray light on the surface of the object to be detected by using a photoelectric detector, and converting the optical signal into an electric signal;
and demodulating the electric signal by using a signal processing unit to detect the stray light level on the surface of the object to be detected.
Priority Applications (1)
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| CN101050996A (en) * | 2006-04-07 | 2007-10-10 | 鸿富锦精密工业（深圳）有限公司 | Detecting device and method for lens stray light |
| CN100427875C (en) * | 2006-10-27 | 2008-10-22 | 清华大学 | Laser confocal feedback micro measuring device |
| CN101452200B (en) * | 2007-11-30 | 2010-11-10 | 鸿富锦精密工业（深圳）有限公司 | Lens stray light detecting system |
| TWI340824B (en) * | 2007-12-26 | 2011-04-21 | Hon Hai Prec Ind Co Ltd | Measuring system for stray light of lens |
| CN100559284C (en) * | 2008-01-21 | 2009-11-11 | 上海微电子装备有限公司 | A kind of method for automatic measurement of heterogeneous light of photo-etching machine |
| US8481904B2 (en) * | 2011-01-07 | 2013-07-09 | Daniel R. Marshall | Autofocus system with stray light compensation |
| CN102944533B (en) * | 2012-11-26 | 2014-11-19 | 中国科学院长春光学精密机械与物理研究所 | Portable stray light detection device of center shielding structure |
| CN102944564A (en) * | 2012-11-26 | 2013-02-27 | 中国科学院长春光学精密机械与物理研究所 | Portable stray light detection device of double far center inclined lighting structure |
| CN103135368A (en) * | 2013-03-14 | 2013-06-05 | 中国科学院光电技术研究所 | Method and system for measuring stray light |
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